Definition 16 ([1]}) 
Let \(G = (V, E)\)  be an arbitrary graph. If \(C\)  is a set of vertices, such that for each \(\lbrace u, v\rbrace  \in E\)  either \(u \in C\)  or \(v \in C\) , \(C\)  is called a vertex cover of \(G\) .

